Tethered drone for downhole oil and gas wellbore operations

ABSTRACT

According to some embodiments, devices, systems, and methods for conveying downhole oil and gas wellbore tools and performing downhole oil and gas wellbore operations are disclosed. The exemplary devices, systems, and methods may include a tethered drone that substantially disintegrates and/or dissolves into a proppant when shaped charges that the tethered drone carries are detonated. Two or more tethered drones, wellbore tools, and/or data collection devices may be connected in a tethered drone string for efficiently performing wellbore operations and reducing the amount of debris left in the wellbore after such operations.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application of and claims priority to Patent Cooperation Treaty (PCT) Application No. PCT/M2019/000530 filed Mar. 29, 2019, which claims the benefit of U.S. Provisional Patent Application No. 62/690,314 filed Jun. 26, 2018. The entire contents of each application listed above are incorporated herein by reference.

FIELD OF THE DISCLOSURE

Devices, systems, and methods for downhole delivery of one or more wellbore tools in an oil or gas wellbore. More specifically, devices, systems, and methods for improving efficiency of downhole wellbore operations and minimizing debris in the wellbore from such operations.

BACKGROUND OF THE DISCLOSURE

Hydraulic Fracturing (or, “fracking”) is a commonly-used method for extracting oil and gas from geological formations (i.e., “hydrocarbon formations”) such as shale and tight-rock formations. Fracking typically involves, among other things, drilling a wellbore into a hydrocarbon formation; deploying a perforating gun including shaped explosive charges in the wellbore via a wireline; positioning the perforating gun within the wellbore at a desired area; perforating the wellbore and the hydrocarbon formation by detonating the shaped charges; pumping high hydraulic pressure fracking fluid into the wellbore to force open perforations, cracks, and imperfections in the hydrocarbon formation; delivering a proppant material (such as sand or other hard, granular materials) into the hydrocarbon formation to hold open the perforations and cracks through which hydrocarbons flow out of the hydrocarbon formation; and, collecting the liberated hydrocarbons via the wellbore.

Perforating the wellbore and the hydrocarbon formations is typically done using one more perforating guns. For example, as shown in FIG. 1 and further described in U.S. Pat. No. 9,494,021 which is incorporated herein by reference in its entirety, a conventional perforating gun string 100 may have two or more perforating guns 110. Each perforating gun 110 may have a substantially cylindrical carrier body 120 housing a charge carrier 130 including, among other things, one more shaped charges 140, a detonating cord 150 for detonating the shaped charges 140, and a conductive line 160 for relaying an electrical signal between connected perforating guns 110. In such “enclosed” perforating guns 110, the carrier body 120 may use, for example, a variety of seals and connections (unnumbered) to prevent the charge carrier 130, shaped charges 140, and other internal components from being exposed to harsh wellbore conditions which may include damaging temperatures, pressures, fluids, corrosive materials, etc. Exposure to such conditions may, for example, deactivate or destroy the perforating gun 110 and associated components or cause premature detonation.

Another known perforating gun type is an “exposed” perforating gun 200, as shown in FIG. 2. The exposed perforating gun 200 includes a charge carrier 220 with a plurality of encapsulated shaped charges 210. The encapsulated shaped charges 210 are exposed to the surrounding environment. Thus, the encapsulated shaped charges 210 may include a structure and/or material that substantially isolates and seals the internal components of the encapsulated shaped charge 210 from external conditions. The exposed perforating gun 200 also includes a conductive line 250 for relaying an electrical signal along the length of the perforating gun 200 and a detonating cord 230 for detonating the encapsulated shaped charges 210. The conductive line 250 and the detonating cord 230 are exposed to external conditions. Thus, the conductive line 250 and the detonating cord 230 must be configured to withstand the temperatures, pressures, and materials that are found within a wellbore. In addition, as shown in FIG. 2, the exposed perforating gun 200 includes a firing head 240 that will initiate the detonating cord 230 upon activation. Multiple exposed perforating guns 200 may also be connected in a gun string.

Gun strings including multiple perforating guns help to improve operational efficiency by allowing multiple perforating intervals to be perforated during one wireline run into the wellbore. The gun string may also include wellbore tools such as one or more fracking plugs (“frac plug”) or bridge plugs, tubing cutters, etc. for downhole operations. For ease of reference in this disclosure, a “gun string” may include any combination of perforating guns and wellbore tools, which further encompasses control devices and the like for use in downhole wellbore operations. Each of the individual perforating guns and/or wellbore tools in the string may have selective detonation/initiation capability. By “selective” what is meant is that a detonator or initiator assembly of an individual perforating gun or wellbore tool is configured to receive one or more specific digital sequence(s), which differs from a digital sequence that might be used to arm and/or detonate another detonator or initiator assembly in a different, adjacent perforating gun or tool. So, detonation of the various perforating guns and/or tools does not necessarily have to occur in a pre-programmed sequence. Any specific perforating gun or tool can be selectively detonated/initiated. The detonation/initiation of perforating guns typically occurs in a bottom-up sequence, i.e., from the perforating gun (or wellbore tool) that is farthest from the wireline to the perforating gun (or wellbore tool) that is nearest, or connected to, the wireline. Thus, in operation, the gun string is lowered or pumped down into the wellbore to a desired location, one or more of the perforating guns and/or tools is detonated/initiated, and the wireline is retracted to the next desired location at which additional perforating gun(s) and/or tool(s) are detonated/initiated. The process repeats until all of the operations have been completed. The wireline cable is then retracted to the surface of the wellbore along with any components that have remained attached to the gun string. Additional debris that remains in the wellbore may need to be recovered as well.

Accordingly, current wellbore operations and system(s) require substantial amounts of onsite personnel and equipment and sometimes result in large residual debris post perforation in the wellbore. Even with selective gun strings, a substantial amount of time, equipment, and labor may be required to deploy the perforating gun or wellbore tool string, position the perforating gun or wellbore tool string at the desired location(s), and remove residual debris post perforating. Further, current perforating devices and systems may be made from materials that remain in the wellbore after detonation of the shaped charges and leave a large amount of debris that must be removed from the wellbore. Accordingly, devices, systems, and methods that may reduce the time, equipment, labor, and debris associated with downhole operations would be beneficial.

BRIEF DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

In an aspect, an exemplary single-piece, self-contained tethered drone comprises: a body portion; a head portion extending from the body portion and including an integrated electrical and mechanical connecting assembly; a tail portion extending from the body portion in a direction opposite the head portion; a wellbore data collection device housed within the drone and configured for electrically connecting to a wireline; and at least one shaped charge, wherein the tethered drone is formed at least in part from a material that will substantially disintegrate upon detonating the shaped charge, while the wellbore data collection device remains intact and operable for delivering the collected data.

In another aspect, an exemplary single-piece, self-contained tethered drone comprises: a body portion; a head portion extending from the body portion; a tail portion extending from the body portion in a direction opposite the head portion and configured for connecting to a wireline, wherein the tail portion includes an electrical transfer contact and circuitry for receiving an electrical signal from a control unit via the wireline; a detonator and optionally, a detonating cord coupled to the detonator, wherein the circuitry transmits the electrical signal to the detonator; and a plurality of shaped charges received in shaped charge apertures in the body portion, wherein the shaped charge apertures are respectively positioned adjacent to at least one of the detonator and the detonating cord within an interior of the body portion, wherein the tethered drone is formed at least in part from a material that will substantially disintegrate upon detonating the shaped charge.

In a further aspect, an exemplary tethered drone string for downhole delivery of one or more wellbore tools comprises: a first single-piece, self-contained tethered drone connected to a second single-piece, self-contained tethered drone, the first tethered drone and the second tethered drone respectively including a body portion, a head portion, a tail portion, and at least one shaped charge, wherein the head portion of the first tethered drone extends from the body portion of the first tethered drone in a direction towards the second tethered drone and includes an integrated electrical and mechanical connecting assembly, the tail portion of the first tethered drone extends from the body portion of the first tethered drone in a direction opposite the head portion and includes a tail connecting portion, wherein the tail connecting portion of the first tethered drone is configured for at least one of connecting to a wellbore tool and connecting to a wireline, the tail portion of the second tethered drone includes a tail connecting portion, wherein the tail connecting portion of the second tethered drone is electrically and mechanically connected to the integrated electrical and mechanical connecting assembly of the first tethered drone, and the head portion of the first tethered drone, alone, provides an electrical transfer and mechanical coupling between the first tethered drone and the second tethered drone via the integrated electrical and mechanical connecting assembly; and a wellbore data collection device configured for at least one of forming a connection between the first tethered drone and the second tethered drone, forming a connection between at least one of the first tethered drone and the second tethered drone respectively and the wireline, and being housed within at least one of the first tethered drone and the second tethered drone, wherein the first tethered drone and the second tethered drone are formed at least in part from a material that will substantially disintegrate upon detonating the shaped charge, while the wellbore data collection device remains intact and operable for delivering the collected data.

For purposes of this disclosure, a “drone” is a self-contained, autonomous or semi-autonomous vehicle for downhole delivery of a wellbore tool. For purposes of this disclosure and without limitation, “autonomous” means without a physical connection or manual control and “semi-autonomous” means without one of a physical connection or manual control.

BRIEF DESCRIPTION OF THE DRAWINGS

A more particular description will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments thereof and are not therefore to be considered to be limiting of its scope, exemplary embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

FIG. 1 is a perspective view of a prior art perforating gun string;

FIG. 2 is a perspective view of a prior art exposed perforating gun;

FIG. 3A is a perspective view of a tethered drone according to an exemplary embodiment;

FIG. 3B is another perspective view of the exemplary embodiment shown in FIG. 3A;

FIG. 4 is a perspective view of a tethered drone string according to an exemplary embodiment;

FIG. 5A is a lateral cross-sectional depiction of a conductive detonating cord for use with the tethered drone according to an exemplary embodiment;

FIG. 5B is a longitudinal cross-sectional depiction of the conductive detonating cord of FIG. 5A;

FIG. 5C is a lateral cross-sectional depiction of another conductive detonating cord for use with the tethered drone according to an exemplary embodiment;

FIG. 5D is a longitudinal cross-sectional depiction of the conductive detonating cord of FIG. 5C;

FIG. 6 illustrates a wellbore perforating system according to an exemplary embodiment;

FIG. 7 is a cross-sectional view of a wireless detonator for use with the tethered drone according to an exemplary embodiment; and

FIG. 8 is a lateral cross-sectional depiction of a tethered drone and arrangement of shaped charges according to an exemplary embodiment.

Various features, aspects, and advantages of the embodiments will become more apparent from the following detailed description, along with the accompanying figures in which like numerals represent like components throughout the figures and text. The various described features are not necessarily drawn to scale but are drawn to emphasize specific features relevant to some embodiments.

The headings used herein are for organizational purposes only and are not meant to limit the scope of the description or the claims. To facilitate understanding, reference numerals have been used, where possible, to designate like elements common to the figures.

DETAILED DESCRIPTION

Reference will now be made in detail to various exemplary embodiments. Each example is provided by way of explanation and is not meant as a limitation and does not constitute a definition of all possible embodiments.

With reference to FIGS. 3A and 3B, an exemplary embodiment of a tethered drone 300 is shown. As described herein, the tethered drone 300 may be conveyed via a wireline 620 (FIG. 6) into a wellbore 670 (FIG. 6), for downhole delivery of one or more wellbore tools such as, for example and without limitation, shaped charges, a frac plug, a tubing cutter, and a wellbore data collection system. The exemplary tethered drone 300 shown in FIGS. 3A and 3B includes a body portion 310 having a front end 311 and a rear end 312. A head portion 320 extends from the front end 311 of the body portion 310 and a tail portion 330 extends from the rear end 312 of the body portion 310 in a direction opposite the head portion 320. In an aspect, the head portion 320 includes a head connecting portion 360 and the tail portion 330 includes a tail connecting portion 370 for connecting a first tethered drone to a second tethered drone in a tethered drone string 400, described below with respect to FIG. 4, or to, for example and without limitation, a wellbore tool or data collection system. The body portion 310 includes a plurality of shaped charge apertures 313 and open apertures 316 extending between an external surface 315 of the body portion 310 and an interior 314 of the body portion 310. Each of the plurality of shaped charge apertures 313 are configured for receiving and retaining a shaped charge 340. The purpose and configuration of the shaped charge apertures 313 and the open apertures 316 will be further described below.

In the exemplary embodiment shown in FIGS. 3A and 3B, the body portion 310, the head portion 320, and the tail portion 330 may be formed from a material that will substantially disintegrate upon detonation of the shaped charges 340. In an exemplary embodiment, the material may be an injection-molded plastic that will substantially dissolve into a proppant when the shaped charges 340 are detonated. In the same or other embodiments, one or more portions of the tethered drone 300 may be formed from a variety of techniques and/or materials including, for example and without limitation, injection molding, casting (e.g., plastic casting and resin casting), metal casting, and 3D printing. Reference to the exemplary embodiments including injection-molded plastics is thus not limiting. A tethered drone 300 formed according to this disclosure leaves a relatively small amount of debris in the wellbore post perforation. In certain exemplary embodiments, one or more of the body portion 310, the head portion 320, and the tail portion 330 may be formed from plastic that is substantially depleted of other components including metals. Substantially depleted may mean, for example and without limitation, lacking entirely or including only nominal or inconsequential amounts. In other embodiments, the plastic may be combined with any other materials consistent with this disclosure. For example, the materials may include metal powders, glass beads or particles, known proppant materials, and the like that may serve as a proppant material when the shaped charges 340 are detonated. In addition, the materials may include, for example, oil or hydrocarbon-based materials that may combust and generate pressure when the shaped charges 340 are detonated, synthetic materials potentially including a fuel material and an oxidizer to generate heat and pressure by an exothermic reaction, and materials that are dissolvable in a hydraulic fracturing fluid.

In the exemplary disclosed embodiments, the body portion 310 is a unitary structure that may be formed from an injection-molded material. In the same or other embodiments, at least two of the body portion 310, the head portion 320, and the tail portion 330 are integrally formed from an injection-molded material. In other embodiments, the body portion 310, the head portion 320, and the tail portion 330 may constitute modular components or connections.

As shown in FIGS. 3A and 3B, each of the body portion 310, the head portion 320, and the tail portion 330 is substantially cylindrically-shaped. The head portion 320 and the tail portion 330 each have a maximum diameter that is greater than a maximum diameter of the body portion 310, and at least a portion of each of the head portion 320 and the tail portion 330 extends beyond the maximum diameter of the body portion 310. The exemplary disclosed configuration may help protect the body portion 310, the shaped charges 340, and the internal components of the body portion 310 from collisions and fluid pressures during the descent of the tethered drone 300 into the wellbore 670. For example, the larger diameter of the head portion 320 and tail portion 330 may block the body portion 310 from collisions and force fluid pressure away from the body portion 310. Each of the head portion 320 and the tail portion 330 also includes fins 373 configured for reducing friction during the descent of the tethered drone 300 into the wellbore 670.

With continuing reference to FIGS. 3A and 3B, each of the plurality of shaped charge apertures 313 in the body portion 310 may receive and retain a portion of a shaped charge 340 in a corresponding hollow portion (unnumbered) of the interior 314 of the body portion 310. Another portion of the shaped charge 340 remains exposed to the surrounding environment. Thus, the body portion 310 may be considered in some respects as an exposed charge carrier, and the shaped charges 340 may be encapsulated, pressure sealed shaped charges having a lid or cap. The plurality of open apertures 316 may be configured for, among other things, reducing friction against the body portion 310 as the tethered drone 310 is conveyed into a wellbore 670 and/or for enhancing the collapse/disintegration properties of the body portion 310 when the shaped charges 340 are detonated.

The interior 314 of the body portion 310 may have hollow regions and non-hollow regions. As discussed above, the shaped charge apertures 313 receive and retain a portion of the shaped charge 340 in a hollow portion of the interior 314 of the body portion 310. Other regions of the interior 314 may be formed as non-hollow or may include additional internal components of the tethered drone 300 as applications dictate. While the shaped charge apertures 313 (and correspondingly, the shaped charges 340) are shown in a typical helical arrangement about the body portion 310 in the exemplary embodiment shown in FIGS. 3A and 3B, the disclosure is not so limited and it is contemplated that any arrangement of one or more shaped charges 340 may be accommodated, within the spirit and scope of this disclosure, by the tethered drone 300. For example, a single shaped charge aperture or a plurality of shaped charge apertures for respectively receiving a shaped charge may be positioned at any phasing (i.e., circumferential angle) on the body portion, and a plurality of shaped charge apertures may be included, arranged, and aligned in any number of ways. For example, and without limitation, the shaped charge apertures 313 may be arranged, with respect to the body portion, along a single longitudinal axis, within a single radial plane, in a staggered or random configuration, spaced apart along a length of the body portion, pointing in opposite directions, or the like. An embodiment of a tethered drone 800 with shaped charges 840 in a planar radial arrangement according to this disclosure is shown in FIG. 8 (discussed below), which is a lateral cross-sectional view of a body portion 810 of such embodiment at a line corresponding to line X shown in FIG. 3A, although not limited thereto.

The body portion 310 of the exemplary tethered drone 300 also houses the detonating cord 350 for detonating the shaped charges 340 and relaying ballistic energy along the length of the tethered drone 300. In the exemplary embodiment shown in FIGS. 3A and 3B, the detonating cord 350 is housed within the interior 314 of the body portion and is exposed to the surrounding environment through the open apertures 316. Accordingly, the detonating cord 350 is configured for withstanding the conditions and materials within a wellbore, without becoming destroyed or inoperable, or detonating prematurely. Such exposed detonating cords are known.

In some embodiments, and depending on the arrangement of the shaped charge apertures 313 and shaped charges 340, the detonating cord 350 may be arranged in a complementary manner to ensure that the detonating cord 350 is in sufficient contact or proximity to the shaped charges 340, for detonating the shaped charges 340.

In an aspect, the body portion 310 of the tethered drone 300 also houses a conductive line (not shown) for relaying an electrical signal along the length of the tethered drone 300, as discussed further below. In the exemplary embodiment shown in FIGS. 3A and 3B, the detonating cord 350 is a conductive detonating cord and includes the conductive line. In other embodiments, the conductive line and the detonating cord 350 may be separate components. An exemplary conductive detonating cord 350 according to the exemplary embodiments is discussed and shown with respect to FIGS. 5A-5D and described in U.S. patent application Ser. No. 16/152,933 filed Oct. 5, 2018, which is incorporated herein by reference in its entirety. The conductive detonating cord 350 is configured for being in electrical communication at one end with an electrical transfer contact 371 a in the tail connecting portion 370, and at an opposite end with an electrical transfer contact such as a pin contact 365 in the head connecting portion 360. In the exemplary embodiment shown in FIG. 3B, the electrical transfer contact 371 a may be an electrical contact or “line in” on a detonator 371, as discussed further below. In such case, the conductive detonating cord 350 and/or conductive component of the conductive detonating cord 350 (or, the conductive line in embodiments where the conductive line and detonating cord are separate components) may be in electrical communication with the electrical transfer contact 371 a via a “line out” on the detonator 371. In the same or other embodiments, electrical transfer contact 371 a may be at least a part of an electrical relay to a line in of a detonator and/or a conductive line or conductive detonating cord. The conductive detonating cord 350 in the exemplary embodiments transfers an electrical signal along the length of the tethered drone from the electrical transfer contact 371 a of the tail connecting portion 370 to the pin contact 365 in the head connecting portion 360. The electrical signal may be provided to the electrical transfer contact 371 a of the tail connecting portion 370 by the wireline 620 or an upstream tethered drone that is connected to the tail connecting portion 370 in a tethered drone string 400, as described below with respect to FIG. 4. The electrical signal may provide, among other things, a selective detonation signal for the tethered drone 300. For purposes of this disclosure, “upstream” in a gun string means in a direction towards the wireline 620 and “downstream” means in a direction away from the wireline.

The tail connecting portion 370 in the exemplary embodiments includes the detonator 371, an igniter, or an initiator (collectively, “detonator”) 371 for activating the conductive detonating cord 350 upon receiving the selective detonation signal or communicating downline through the electrically conductive cord. A detonator bulkhead seal 372 may substantially isolate the detonator or a relay/transition from the detonator 371 to the detonating cord 350 from exposure to the wellbore fluid, including the associated high temperatures, pressures, and potentially corrosive components.

In an exemplary embodiment, the detonator 371 may be a wireless detonator assembly as shown in FIG. 7 and further described in U.S. Pat. No. 9,581,422 which is incorporated herein by reference in its entirety. In an exemplary wireless detonator assembly 710 shown in FIG. 7, a detonator shell 712 is shaped as a hollow cylinder and houses at least a detonator head plug 714, a fuse head 715, an electronic circuit board 716, and explosive components 730. The electronic circuit board 716 is connected to the fuse head 715 and is configured for allowing selective detonation of the detonator assembly 710. The electronic circuit board 716 is configured to wirelessly and selectively receive an ignition signal I, (typically a digital code uniquely configured for a specific detonator), to fire a perforating gun.

With continuing reference to FIG. 7, a detonator head 718 extends from one end of the detonator shell 712 and includes more than one electrical contacting component including an electrically contactable line-in portion 720 and an electrically contactable line-out portion 722, according to an aspect. In an exemplary embodiment of the tethered drone 300 including the detonator assembly 710 shown in FIG. 7, line-in portion 720 may serve as the electrical transfer contact 371 a. According to one aspect, the detonator assembly 710 may also include an electrically contactable ground portion 713. The detonator head 718 may be disk-shaped. In an aspect, at least a portion of the detonator shell 712 is configured as the ground portion 713. The detonator head 718 also includes an insulator 724, which is positioned between the line-in portion 720 and the line-out portion 722. The insulator 724 functions to electrically isolate the line-in portion 720 from the line-out portion 722. Insulation may also be positioned between other lines of the detonator head 718. It is possible for all of the contacts to be configured as part of the detonator head 718 (not shown), as found, for instance, in a banana connector used in a headphone wire assembly in which the contacts are stacked longitudinally along a central axis of the connector, with the insulating portion situated between them.

In the exemplary wireless detonator assembly 710, a capacitor 717 is positioned or otherwise assembled as part of the electronic circuit board 716. The capacitor 717 is configured to be discharged to initiate the detonator assembly 710 upon receipt of a digital firing sequence via the ignition signal I, the ignition signal being electrically relayed directly through the line-in portion 720 and the line-out portion 722 of the detonator head 718. The fuse head 715 initiates the explosive load 730. In a typical arrangement, a first digital code is transmitted down-hole to and received by the electronic circuit board 716. Once it is confirmed that the first digital code is the correct code for that specific detonator assembly, an electronic gate is closed and the capacitor 717 is charged. Then, as a safety feature, a second digital code is transmitted to and received by the electronic circuit board 716. The second digital code, which is also confirmed as the proper code for the particular detonator, closes a second gate, which in turn discharges the capacitor 717 via the fuse head 715 to initiate the detonation.

The exemplary detonator assembly 710 according to an aspect can be either an electric or an electronic detonator. In an electric detonator, a direct wire from the surface is electrically contactingly connected to the detonator assembly 710 and power is increased to directly initiate the fuse head 715. In an electronic detonator assembly, circuitry of the electronic circuit board 716 within the detonator assembly is used to initiate the fuse head 715.

With reference again now to FIGS. 3A and 3B and the exemplary tethered drone 300, the tail connecting portion 370 may further include an onboard computer or other circuitry (not shown) for, among other things, receiving the selective detonation signal and other commands from a control unit 630 (see FIG. 6) or capturing information regarding the wellbore such as geometry, distance, temperature, pressure, fluid properties, etc. The tethered drone 300 and associated components may be powered by one or more of a power source conveyed by the wireline 620, one or more batteries in each tethered drone 300, or one or more batteries at the top of a gun string 400 that relays power via the conductive line to each tethered drone 300 in the gun string 400. In some embodiments, the power source may include a capacitor, instead of a single battery pack, charged on surface before the drone is deployed into the wellbore and configured for providing power to the tethered drone and associated components, and/or a data collection device and other wellbore tool(s). Such capacitor may be charged on surface by a power supply configured for electrically connecting to the capacitor, either directly or via one or more electrical relays, and providing a sufficient electric current to load the capacitor. The power supply may take any form consistent with this disclosure. As a safety measure, the wired power source and/or battery(-ies) or other power sources may not be activated until, for example and without limitation, the tethered drone 300 is deployed in the wellbore 670 to a particular distance or for a particular amount of time. Thus, the detonator 371 may not be armed until the tethered drone 300 reaches a safe position and the power/battery(-ies) activate.

The head connecting portion 360 is configured for connecting to and being in electrical contact with a downstream tethered drone or wellbore tool in a tethered drone string 400 as described with respect to FIG. 4. In the exemplary embodiment shown in FIGS. 3A and 3B, the head connecting portion 360 and the tail connecting portion 370 each include a threaded portion 361, 374 that is respectively configured for being threadingly connected to a complimentary connecting portion on an adjacent tethered drone. In other embodiments, the connection between the head connecting portion 360 and the tail connecting portion 370 may be by other known devices or techniques that are consistent with the scope of this disclosure. Additional components such as a wellbore tool or a data collection system with a complimentary threaded connection (or other connection) may also be connected to the tethered drone 300 via the head connecting portion 360 and/or the tail connecting portion 370. For purposes of this disclosure, the exemplary disclosed connections between adjacent tethered drones is representative of connections between a tethered drone 300 and such additional components.

According to an exemplary embodiment, the pin contact 365 of the head connecting portion 360 is configured for being in electrical contact with the electrical transfer contact 371 a of the tail connecting portion 370 of an adjacent tethered drone when the head connecting portion 360 is connected to the tail connecting portion 370 of the adjacent tethered drone. The pin contact 365 is configured to transfer the electrical signal from the conductive line or conductive detonating cord 350 to the electrical transfer contact 371 a of the tail connecting portion 370 of the adjacent tethered drone such that the electrical signal may be provided to, e.g., the detonator 371 or other component(s) of the adjacent tethered drone and/or a conductive line or conductive detonating cord of the adjacent tethered drone. In an aspect, the pin contact 365 may, among other things, also transfer control information, instructions, data, or power from a control unit 630, wireline 620, and/or battery (not illustrated) to the electrical transfer contact 371 a or other onboard computer/circuitry of the tail connecting portion 370 of the adjacent tethered drone. In another aspect, the pin contact 365 may be a spring-loaded pin contact 365 that is biased towards the adjacent tethered drone to maintain electrical contact with the electrical transfer contact 371 a of the tail connecting portion 370 of the adjacent tethered drone. The respective electrical transfer contacts of the head connecting portion 360 and the tail connecting portion 370 are not limited according to this disclosure. The respective electrical transfer contacts of the head connecting portion 360 and the tail connecting portion 370 may take any form or configuration consistent with this disclosure—for example, configured for being in electrical contact when the head connecting portion 360 of a first tethered drone 300 is connected to the tail connecting portion 370 of a second tethered drone 300 and for relaying the electrical signal from the conductive detonating cord 350 of the first tethered drone 300 to, e.g., the detonator 371 or other component(s) of the second tethered drone 300.

With continuing reference to FIGS. 3A and 3B, the exemplary tethered drone 300 may also include a blast barrier 380 positioned between at least a portion of the head portion 320 of the tethered drone 300 and the tail portion (330) of a downstream tethered drone that is attached to the head connecting portion 360 of the tethered drone 300. The blast barrier 380 may be configured for shielding the head portion 320 of the tethered drone 300 from detonation, disintegration, and debris of the downstream tethered drone and preventing destruction and/or disintegration of the head portion 320 of the tethered drone 300 as a result of the downstream detonation. The blast barrier 380 may generally be any shape consistent with this disclosure and may be formed from a variety of materials consistent with this disclosure such as, for example and without limitation, metals and plastics and combinations of those materials. In the same or other embodiments, the head portion 320 of the tethered drone 300 may be formed from a material such as metals, plastics, or combinations of those materials, and/or have a material structure or size configured for resisting disintegration under the force and heat of a downstream detonation.

With reference now to FIG. 4, an exemplary tethered drone string 400 is shown. Two or more tethered drones 401, 402 may be connected to form a tethered drone string 400. Each of a first tethered drone 401 and a second tethered drone 402 is an exemplary tethered drone as described above with respect to FIGS. 3A and 3B and includes a body portion 410, 411, a head portion 420, 421 having a head connecting portion 460, and a tail portion 430, 431 having a tail connecting portion 470. Each of the first tethered drone 401 and the second tethered drone 402 carries shaped charges 440, 441 in the body portion 410, 411 as discussed with respect to FIGS. 3A and 3B. The head connecting portion 460 (not visible in the illustration of FIG. 4) of the first tethered drone 401 is connected to the tail connecting portion 470 (not visible in the illustration of FIG. 4) of the second tethered drone 402. In the same or other embodiments, the head connecting portion 460 or the tail connecting portion 470 of a tethered drone 401, 402 in a drone string 400 may be connected to, for example and without limitation, a wellbore tool or a data collection system.

The head connecting portion 420, 421 of each of the first tethered drone 401 and the second tethered drone 402 in the exemplary embodiment shown in FIG. 4 includes, among other things, an electrical transfer contact such as the pin contact 365 (not visible in FIG. 4) as discussed with respect to FIGS. 3A and 3B. The tail connecting portion 430, 431 of each of the first tethered drone 401 and the second tethered drone 402 includes, among other things, a detonator 471 and an electrical transfer contact 471 a as also discussed with respect to FIGS. 3A and 3B. Accordingly, a conductive detonating cord 450, 451 may relay ballistic energy and an electrical signal along a length of the respective tethered drones 401, 402 from the electrical transfer contact 471 a (in an embodiment, via the line out connection of a detonator assembly or an appropriate relay) of the tail connecting portion 470 to the pin contact 365 in the same manner as discussed with respect to the exemplary embodiment shown in FIGS. 3A and 3B. In the exemplary embodiment shown in FIG. 4, the pin contact 365 of the first tethered drone 401 is in electrical contact with the electrical transfer contact 471 a of the tail connecting portion 470 of the second tethered drone 402.

In use, the first tethered drone 401 may be the topmost tethered drone in the tethered drone string 400; i.e., the tethered drone that is connected to the wireline 620 or, for example and without limitation, a wellbore tool, a firing head, an electronic control component, one or more batteries, or the like that is connected between the wireline 620 and the first tethered drone 401. In any such embodiment, an electrical transfer contact of the wireline 620 or other component is configured for being in electrical contact with the electrical transfer contact 471 a of the tail connecting portion 470 of the first drone 401. In an aspect, an electrical signal constituting a selective detonation signal may be sent from the control unit 630 at a surface 601 of the wellbore 670 and conveyed via the wireline 620 to the electrical transfer contact 471 a of the tail connecting portion 470 of the first tethered drone 401. The selective detonation signal may be configured to activate the detonator 471 of a downstream tethered drone 402 or wellbore tool. Thus, the detonator 471 of the first tethered drone 401 will not be activated by the selective detonation signal. The conductive detonating cord 450 of the first tethered drone 401 will relay the selective detonation signal from the electrical transfer contact 471 a of the tail connecting portion 470 of the first tethered drone 401 to the pin contact 365 of the first tethered drone 401. The pin contact 365 of the first tethered drone 401 will transfer the selective detonation signal to the electrical transfer contact 471 a of the tail connecting portion 470 of the second tethered drone 402. If the selective detonation signal corresponds to the second tethered drone 402, the detonator 471 of the second tethered drone 402 will activate and ballistically initiate the conductive detonating cord 451 to detonate the shaped charges 441 that the second tethered drone 402 carries. The process will repeat for each tethered drone and/or wellbore tool in the tethered drone string 400. According to the exemplary embodiment of the tethered drone 300, each tethered drone 401, 402 in the drone string 400 may be formed from an injection-molded plastic material that will substantially disintegrate and/or dissolve into a proppant upon detonation of the shaped charges 440, 441, thereby reducing the amount of debris generated by successive detonations of the tethered drones 401, 402.

Notably, the configuration of the tethered drone string 400 and, in particular, the conductive line (for example, in the conductive detonating cord 450, 451 of the exemplary embodiments) allows a single power source, such as a single battery at the top of the tethered drone string 400, to provide power to each tethered drone 401, 402 and/or wellbore tool in the tethered drone string 400. The power may be relayed between each tethered drone 401, 402 and/or wellbore tool via the conductive detonating cords 450, 451 in the same manner as, e.g., the selective detonation signal.

With reference now to FIGS. 5A-5D, FIGS. 5A and 5B respectively show a lateral cross-section and a longitudinal cross-section of a first exemplary embodiment of a conductive detonating cord 10 for use with the exemplary tethered drone 300, and FIGS. 5C and 5D respectively show a lateral cross-section and a longitudinal cross-section of a second exemplary embodiment of a conductive detonating cord 10 for use with the exemplary tethered drone 300. The conductive detonating cord 10 may be a flexible structure that allows the conductive detonating cord 10 to be bent or wrapped around structures. According to an aspect, the conductive detonating cord 10 may include a protective structure or sheath 16 that prevents the flow of an extraneous or stray electric current through an explosive layer 14 within the conductive detonating cord 10. The explosive layer 14 may include an insensitive secondary explosive (i.e., an explosive that is less sensitive to electrostatic discharge (ESD), friction and impact energy within the detonating cord, as compared to a primary explosive). According to an aspect, the explosive layer 14 includes at least one of pentaerythritol tetranitrate (PETN), cyclotrimethylenetrinitramine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine/cyclotetramethylene-tetranitramine (HMX), Hexanitrostilbene (HNS), 2,6-Bis(picrylamino)-3,5-dinitropyridine (PYX), and nonanitroterphenyl (NONA). The type of material selected to form the explosive layer 14 may be based at least in part on the temperature exposure, radial output and detonation velocity of the material/explosive. In an embodiment, the explosive layer 14 includes a mixture of explosive materials, such as, HNS and NONA. As would be understood by one of ordinary skill in the art, the explosive layer 14 may include compressed explosive materials or compressed explosive powder. The explosive layer 14 may include constituents to improve the flowability of the explosive powder during the manufacturing process. Such constituents may include various dry lubricants, such as, plasticizers, graphite, and wax.

The conductive detonating cord 10 further includes an electrically conductive layer 12. The electrically conductive layer 12 is configured to transfer a communication signal along a length L of the conductive detonating cord 10. The communication signal may be a telemetry signal. According to an aspect, the communication signal includes at least one of a signal to check and count for detonators in a perforating gun string assembly, address and switch to certain detonators, charge capacitors, send a signal to initiate a detonator communicably connected to the conductive detonating cord 10, and various other functions as described in this disclosure. The integration of the electrically conductive layer 12 in the conductive detonating cord 10 helps to omit conductive lines as a separate component.

According to an aspect, the electrically conductive layer 12 extends around the explosive layer 14 in a spaced apart configuration. An insulating layer 18 (FIGS. 5C and 5D) may be sandwiched between the explosive layer 14 and the electrically conductive layer 12. The electrically conductive layer 12 of the detonating cord 10 may include a plurality of electrically conductive threads/fibers spun or wrapped around the insulating layer 18, or an electrically conductive sheath/pre-formed electrically conductive sheath 13 in a covering relationship with the insulating layer 18. According to an aspect, the electrically conductive sheath 13 comprises layers of electrically conductive woven threads/fibers that are pre-formed into a desired shape that allows the electrically conductive sheath to be easily and efficiently placed or arranged over the insulating layer 18. The layers of electrically conductive woven threads may be configured in a type of crisscross or overlapping pattern in order to minimize the effective distance the electrical signal must travel when it traverses through the conductive detonating cord 10. This arrangement of the threads helps to reduce the electrical resistance (Ohm/ft or Ohm/m) of the conductive detonating cord 10. The electrically conductive threads and the electrically conductive woven threads may include metal fibers or may be coated with a metal, each metal fiber or metal coating having a defined resistance value (Ohm/ft or Ohm/m). It is contemplated that longer gun strings (i.e., more perforating guns in a single string) may be formed using perforating guns that include the conductive detonating cord 10.

FIGS. 5C and 5D illustrate the conductive detonating cord 10 including the insulating layer 18. The insulating layer 18 is disposed/positioned between the explosive layer 14 and the electrically conductive layer 12. As illustrated in FIG. 5D, for example, the insulating layer 18 may extend along the length L of the conductive detonating cord 10. In other embodiments, the insulating layer 18 may only extend along a portion of the length L of the detonating cord and the explosive layer 14 may be adjacent to the electrically conductive layer 12. The insulating layer 18 may be formed of any nonconductive material. According to an aspect, the insulating layer 18 may include at least one of a plurality of non-conductive aramide threads, a polymer, such as fluorethylenpropylene (FEP), polyamide (PA), polyethylenterephthalate (PET), or polyvinylidenfluoride (PVDF), and a coloring additive.

The conductive detonating cord 10 may include a layer of material along its external surface to impart additional strength and protection to the structure of the conductive detonating cord 10. FIGS. 5A-5D each illustrate a jacket/outer protective jacket 16 externally positioned on the conductive detonating cord 10. According to an aspect, the jacket 16 is formed of at least one layer of woven threads. The jacket 16 may be formed from a nonconductive polymer material, such as FEP, PA, PET, and PVDF. According to an aspect, the jacket 16 is formed of at least one layer of non-conductive woven threads and covered by a sheath formed from a plastic, composite or lead.

As illustrated in FIGS. 5A and 5C, the jacket 16 extends around/surrounds/encases the electrically conductive layer 12/electrically conductive sheath 13, the insulating layer 18, and the explosive layer 14. The jacket 16 extends along the length L of the conductive detonating cord 10, and may be impervious to at least one of sour gas (H₂S), water, drilling fluid, and electrical current.

According to an aspect, electric pulses, varying or alternating current or constant/direct current may be induced into or retrieved from the electrically conductive layer 12/electrically conductive sheath 13 of the conductive detonating cord 10. The conductive detonating cord 10 includes contacts (not shown) that are configured to input a communication signal at a first end of the conductive detonating cord 10, and output the communication signal at a second end of the conductive detonating cord 10. According to an aspect, the contacts may include a metal, such as aluminum, brass, copper, stainless steel or galvanized steel (including zinc). In order to facilitate the communication of the communication signal, the contacts may at least partially be embedded into the conductive detonating cord 10. The contacts may be coupled to or otherwise secured to the conductive detonating cord 10. According to an aspect, the contacts are crimped onto the detonating cord 10, in such a way that the contacts pierce through the protective outer jacket 16 of the conductive detonating cord 10 to engage the electrically conductive layer 12 or the conductive sheath 13. In use with an exemplary tethered drone 300, the contacts are configured without limitation for being in electrical communication with the electrical transfer contact 371 a and the pin contact 365.

With reference now to FIG. 6, an exemplary wellbore operation site and system is illustrated. The site includes a hydrocarbon formation 602 under the surface 601 of the ground/wellbore 670. The wellbore 670 extends into the hydrocarbon formation 602 in both vertical and horizontal directions. A wellbore casing or tubing 660 lines the inside of the wellbore 670. One or more tethered drones 300 according to the exemplary embodiment shown in FIGS. 3A and 3B are conveyed downhole in the wellbore 670 via the wireline 620 in an interior 661 of the tubing/casing 660. A wireline spool 610 at the surface 601 of the wellbore 670 feeds the wireline 620 into the wellbore 670. Upon reaching a desired position within the wellbore 670, the shaped charges 340 of the tethered drone 300 are detonated 640 and perforate 650 the tubing/casing 660 and the hydrocarbon formation 602. The tethered drone(s) 300 are controlled and/or powered by the control unit 630 at the surface 601 of the wellbore 670. In an exemplary embodiment, the control unit 630 may communicate unidirectionally with the tethered drone via a relay on the wireline 620. In other embodiments, the control unit 630 and the tethered drone may communicate bi-directionally and/or via a wireless link.

With reference now to FIG. 8, the lateral cross-sectional view of the exemplary tethered drone 800 including shaped charges 840 arranged in a planar radial configuration, as discussed with respect to FIG. 3A, is shown. The lateral cross-sectional view is taken through the body portion in the direction indicated by line X in FIG. 3A, although not limited to the position or configuration shown in FIG. 3A. The lateral cross-sectional view of the exemplary tethered drone shown in FIG. 8 bisects three shaped charges 840 arranged in the same radial plane with respect to the body portion 810 and spaced apart by about a 120-degree phasing around the body portion 810. As previously discussed, the shaped charges 840 are respectively received and retained in shaped charge apertures 813 at least in part within an interior 814 of the body portion 810. In the exemplary configuration shown in FIG. 8, a detonator 871 for detonating the shaped charges 840 is positioned within the interior 814 of the body portion 810 and adjacent to the shaped charges 840. The shaped charges 840 extend radially outwardly from the detonator 871. In some embodiments, the shaped charges 840 may be adjacent to and extending radially outwardly from a detonating cord for detonating the shaped charges 840, depending on, e.g., a desired configuration for particular applications. As previously discussed, the planar radial configuration of the shaped charges 840 in the tethered drone 800 embodiment shown in FIG. 8 is not limiting with respect to the embodiments contemplated by this disclosure, nor is the placement or position of a detonator, a detonating cord, or other components of a tethered drone.

The present disclosure, in various embodiments, configurations and aspects, includes components, methods, processes, systems and/or apparatus substantially developed as depicted and described herein, including various embodiments, sub-combinations, and subsets thereof. Those of skill in the art will understand how to make and use the present disclosure after understanding the present disclosure. The present disclosure, in various embodiments, configurations and aspects, includes providing devices and processes in the absence of items not depicted and/or described herein or in various embodiments, configurations, or aspects hereof, including in the absence of such items as may have been used in previous devices or processes, e.g., for improving performance, achieving ease and/or reducing cost of implementation.

The phrases “at least one”, “one or more”, and “and/or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C”, “at least one of A, B, or C”, “one or more of A, B, and C”, “one or more of A, B, or C” and “A, B, and/or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together.

In this specification and the claims that follow, reference will be made to a number of terms that have the following meanings. The terms “a” (or “an”) and “the” refer to one or more of that entity, thereby including plural referents unless the context clearly dictates otherwise. As such, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. Furthermore, references to “one embodiment”, “some embodiments”, “an embodiment” and the like are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term such as “about” is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Terms such as “first,” “second,” “upper,” “lower” etc. are used to identify one element from another, and unless otherwise specified are not meant to refer to a particular order or number of elements.

As used herein, the terms “may” and “may be” indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and/or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of “may” and “may be” indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances the modified term may sometimes not be appropriate, capable, or suitable. For example, in some circumstances an event or capacity can be expected, while in other circumstances the event or capacity cannot occur—this distinction is captured by the terms “may” and “may be.”

As used in the claims, the word “comprises” and its grammatical variants logically also subtend and include phrases of varying and differing extent such as for example, but not limited thereto, “consisting essentially of” and “consisting of.” Where necessary, ranges have been supplied, and those ranges are inclusive of all sub-ranges therebetween. It is to be expected that variations in these ranges will suggest themselves to a practitioner having ordinary skill in the art and, where not already dedicated to the public, the appended claims should cover those variations.

The terms “determine”, “calculate” and “compute,” and variations thereof, as used herein, are used interchangeably and include any type of methodology, process, mathematical operation or technique.

The foregoing discussion of the present disclosure has been presented for purposes of illustration and description. The foregoing is not intended to limit the present disclosure to the form or forms disclosed herein. In the foregoing Detailed Description for example, various features of the present disclosure are grouped together in one or more embodiments, configurations, or aspects for the purpose of streamlining the disclosure. The features of the embodiments, configurations, or aspects of the present disclosure may be combined in alternate embodiments, configurations, or aspects other than those discussed above. This method of disclosure is not to be interpreted as reflecting an intention that the present disclosure requires more features than are expressly recited in each claim. Rather, as the following claims reflect, the claimed features lie in less than all features of a single foregoing disclosed embodiment, configuration, or aspect. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of the present disclosure.

Advances in science and technology may make substitutions possible that are not now contemplated by reason of the imprecision of language; these variations should be covered by the appended claims. This written description uses examples to disclose the method, machine and computer-readable medium, including the best mode, and also to enable any person of ordinary skill in the art to practice these, including making and using any devices or systems and performing any incorporated methods. The patentable scope thereof is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if, for example, they have structural elements that do not differ from the literal language of the claims, or if they include structural elements with insubstantial differences from the literal language of the claims. 

1. A single-piece, self-contained tethered drone, comprising: a body portion; a head portion extending from the body portion and including an integrated electrical and mechanical connecting assembly; a tail portion extending from the body portion in a direction opposite the head portion; a wellbore data collection device housed within the drone and configured for electrically connecting to a wireline; and at least one shaped charge, wherein the tethered drone is formed at least in part from a material that will substantially disintegrate upon detonating the shaped charge, while the wellbore data collection device remains intact and operable for delivering the collected data.
 2. The tethered drone of claim 1, further comprising a detonator and optionally, a detonating cord coupled to the detonator, and a plurality of shaped charges received in shaped charge apertures in the body portion, wherein the shaped charge apertures are respectively positioned adjacent to at least one of the detonator and the detonating cord within an interior of the body portion.
 3. The tethered drone of claim 2, further comprising circuitry positioned within the tail portion and programmed to receive a selective detonation signal from a control unit via the wireline and to transmit the selective detonation signal to the detonator.
 4. The tethered drone of claim 3, wherein the integrated electrical and mechanical connecting assembly includes an electrically conductive pin connector and a mechanical connector respectively configured for connecting to a complementary electrical component and a complementary mechanical connector.
 5. The tethered drone of claim 4, further comprising a conductive wire configured for relaying an electrical signal along a length of the tethered drone from the circuitry to the pin connector.
 6. The tethered drone of claim 5, wherein the complementary electrical component and the complementary mechanical connector are parts of a complementary drone separate and distinct from the tethered drone, and the integrated electrical and mechanical connecting assembly of the head portion of the tethered drone is configured for electrically connecting the pin connector of the integrated electrical and mechanical assembly to the complementary electrical component of the complementary drone when the mechanical connector of the integrated electrical and mechanical assembly is connected to the complementary mechanical connector of the complementary drone to connect the tethered drone to the complementary drone, and the head portion, alone, provides an electrical transfer and mechanical coupling for connecting the tethered drone to the complementary drone via the conductive wire, the pin connector, and the mechanical connector.
 7. The tethered drone of claim 5, wherein the conductive wire is configured for receiving the electrical signal from the wireline via a direct connection or through one or more electrically conductive components.
 8. The tethered drone of claim 1, wherein the wellbore data collection device is configured for receiving at least one of a power supply and an electrical signal from the wireline via a direct connection or through one or more electrically conductive components.
 9. The tethered drone of claim 1, wherein the wellbore data collection device is the only removeable component of the tethered drone after detonating the shaped charge, and the wellbore data collection device is configured for being removed from the wellbore by the wireline.
 10. A single-piece, self-contained tethered drone, comprising: a body portion; a head portion extending from the body portion; a tail portion extending from the body portion in a direction opposite the head portion and configured for connecting to a wireline, wherein the tail portion includes an electrical transfer contact and circuitry for receiving an electrical signal from a control unit via the wireline; a detonator and optionally, a detonating cord coupled to the detonator, wherein the circuitry transmits the electrical signal to the detonator; and a plurality of shaped charges received in shaped charge apertures in the body portion, wherein the shaped charge apertures are respectively positioned adjacent to at least one of the detonator and the detonating cord within an interior of the body portion, wherein the tethered drone is formed at least in part from a material that will substantially disintegrate upon detonating the shaped charge.
 11. The tethered drone of claim 10, wherein the head portion includes an integrated electrical and mechanical connecting assembly, and the head portion, alone, provides an electrical transfer and mechanical coupling for electrically and mechanically connecting the tethered drone to a complementary electrical component and a complementary mechanical component of a complementary drone separate and distinct from the tethered drone.
 12. A tethered drone string for downhole delivery of one or more wellbore tools, comprising: a first single-piece, self-contained tethered drone connected to a second single-piece, self-contained tethered drone, the first tethered drone and the second tethered drone respectively including a body portion, a head portion, a tail portion, and at least one shaped charge, wherein the head portion of the first tethered drone extends from the body portion of the first tethered drone in a direction towards the second tethered drone and includes an integrated electrical and mechanical connecting assembly, the tail portion of the first tethered drone extends from the body portion of the first tethered drone in a direction opposite the head portion and includes a tail connecting portion, wherein the tail connecting portion of the first tethered drone is configured for at least one of connecting to a wellbore tool and connecting to a wireline, the tail portion of the second tethered drone includes a tail connecting portion, wherein the tail connecting portion of the second tethered drone is electrically and mechanically connected to the integrated electrical and mechanical connecting assembly of the first tethered drone, and the head portion of the first tethered drone, alone, provides an electrical transfer and mechanical coupling between the first tethered drone and the second tethered drone via the integrated electrical and mechanical connecting assembly; and a wellbore data collection device configured for at least one of forming a connection between the first tethered drone and the second tethered drone, forming a connection between at least one of the first tethered drone and the second tethered drone respectively and the wireline, and being housed within at least one of the first tethered drone and the second tethered drone, wherein the first tethered drone and the second tethered drone are formed at least in part from a material that will substantially disintegrate upon detonating the shaped charge, while the wellbore data collection device remains intact and operable for delivering the collected data.
 13. The tethered drone string of claim 12, wherein the first tethered drone and the second tethered drone respectively include a detonator and optionally, a detonating cord coupled to the detonator, and a plurality of shaped charges received in shaped charge apertures in the body portion, wherein the shaped charge apertures are respectively positioned adjacent to at least one of the detonator and the detonating cord within an interior of the body portion.
 14. The tethered drone string of claim 13, wherein the first tethered drone alone includes circuitry positioned within the tail portion of the first tethered drone and programmed to receive a selective detonation signal from a control unit via the wireline and transmit the selective detonation signal to the respective detonator in each of the first tethered drone and the second tethered drone.
 15. The tethered drone string of claim 14, wherein the first tethered drone further includes a conductive wire configured for relaying the selective detonation signal along a length of the first tethered drone from the circuitry to the integrated electrical and mechanical connecting assembly.
 16. The tethered drone string of claim 15, wherein the integrated electrical and mechanical connecting assembly transfers the selective detonation signal, via the tail connecting portion of the second tethered drone, from the conductive wire to the detonator of the second tethered drone.
 17. The tethered drone string of claim 16, wherein the integrated electrical and mechanical connecting assembly of the first tethered drone includes an electrically conductive pin connector electrically connected to an electrical transfer contact of the tail connecting portion of the second tethered drone and a mechanical connector connected to a complementary mechanical connector of the tail connecting portion of the second tethered drone.
 18. The tethered drone string of claim 17, wherein the mechanical connector of the integrated electrical and mechanical connecting assembly is threadingly connected to the complementary mechanical connector of the tail connecting portion of the second tethered drone.
 19. The tethered drone string of claim 12, further comprising a single battery positioned within the tail portion of the first tethered drone, wherein the single battery provides a power supply to each of the first tethered drone and the second tethered drone.
 20. The tethered drone string of claim 12, wherein the wellbore tool is a wellbore data collection device connected to the tail connecting portion via a complementary connection and configured for connecting to the wireline, further wherein the wellbore data collection device is the only removable component of the tethered drone string after detonating the shaped charges, wherein the wellbore data collection device is configured for being removed from the wellbore by the wireline. 